1. Field of the Invention
The present invention relates to an image measuring system, image measuring method, and image measuring program having a non-stop measurement mode for image measurement, in which an imaging means moves relative to a measuring object supported on a measurement stage and captures instantaneous image information at designated measurement positions without making a stop.
2. Description of the Related Art
A conventional CNC image measuring machine comprises a measurement stage, which is moved relative to an imaging means such as a CCD camera and stopped at a measurement position as shown in FIG. 8. Then, the amount of illuminating light is adjusted to acquire image information about a measuring object. To the acquired image information, image processing such as setting of a measuring tool and edge detection is applied, thereby executing a measurement at one measurement position. This measurement is repeated as Measurement 1, Measurement 2, . . . and so on for all measurement positions to achieve measurements at required positions (hereinafter, such the measurement mode is referred to as a “standard measurement mode”).
In contrast, for the purpose of improving the throughput of measurement, a measurement may be performed without making a stop of the measurement stage relative to the imaging means even at a measurement position in a measurement mode (hereinafter, such the measurement mode is referred to as a “non-stop measurement mode”). An image measuring machine having such the non-stop measurement mode has been proposed (see JP-A2004-535587, paragraphs 0005-0006, FIG. 2). This image measuring machine irradiates the measuring object with strobe illumination, as shown in FIG. 9, without making a stop of the measurement stage at measurement positions. Alternatively, it captures instantaneous image information imaged using a shuttered CCD camera, for image measurement. In the non-stop measurement mode, when the relation between the movement speed of the stage and the strobe pulse width is appropriately set, a faster measurement can be achieved as an effect, without lowering the measurement accuracy much.
In the non-stop measurement mode, however, the wider the lightening pulse width of strobe illumination or the open duration of the shutter at the time of capturing the image information about the measuring object (hereinafter referred to as a “duration of capturing image information”), the larger the amount of movement of the stage at the time of image acquisition (the amount of shake of the acquired image) becomes. A larger amount of movement generally worsens the measurement accuracy. On the other hand, imaging the measuring object to acquire image information usable in measurement requires the quantity of illuminating light or the exposure time of the imaging means to be sufficient to a certain extent. From such the viewpoint, the duration of capturing image information should be set to have a necessary and sufficient value.